The invention relates to a method of comparing the amplitudes of two electric signals.
Such comparisons are frequently carried out in all types of electronic circuits, for example, with a view to perform gain controls. It may be easy to compare the amplitudes of two synchronous signals using simple comparators, however, it is a different matter when said signals are out of phase. In the latter case, such signals reach maximum and minimum values at different moments in time and an instantaneous comparison between said signals is no longer representative of their possible difference in amplitude. Most methods enabling such signals to be compared make use of storage stages to store the maximum values of the signals, which in certain cases involves analog-to-digital conversion of said signals in order to store and compare the maximum or minimum values of these signals in digital form. Such methods require complex and hence expensive structures, both in terms of silicon surface area and in terms of energy consumption.
It is an object of the invention to overcome these drawbacks by means of a method which enables amplitudes of two signals to be compared without requiring any storage of these signals.
A method as described in the opening paragraph is characterized in accordance with the invention in that the method includes a stage wherein powers conveyed by said signals are compared.
This method makes use of the fact that the power conveyed by a signal is representative of its amplitude. Thus, in accordance with the invention, it is no longer necessary to simultaneously have the amplitude values of each one of the signals in order to compare them instantaneously, which is difficult when the signals are out of phase. It is sufficient to develop, for each signal, some data representative of the power it conveys, said data being phase-independent.
In accordance with a variant of the invention, a method as described hereinabove is characterized in that it includes a stage wherein a value is generated that is representative of a difference between the mean values of the squares of the amplitudes of these signals.
This method combines, in a single step, the development of data representative of the powers conveyed by the signals, and a comparison between these data.
The method in accordance with the invention can be advantageously used to correct amplitude differences between two signals. In one of its possible applications, the invention thus also relates to a method which cyclically carries out the following operations:
comparison between the amplitudes of said two signals, and
amplification of the signal having the smallest amplitude, and, simultaneously, attenuation of the signal having the highest amplitude,
which method is characterized in that the comparison between the amplitudes of the signals is carried out by means of a method as described hereinabove.
In one of its embodiments, the invention also relates to a device for comparing the amplitudes of a first and a second input signal, characterized in that this device includes means for comparing the powers conveyed by said signals.
In another embodiment, the invention relates to a correction device for correcting a difference in amplitude between a first and a second input signal, comprising:
a device for comparing the amplitudes of the first and the second input signal as described hereinabove, and
a first and a second variable-gain amplifier provided with signal inputs for receiving, respectively, the first and the second input signal, and with signal outputs for supplying its input signals to the comparison device, and with gain control inputs for receiving, from the comparison device, signals which are representative of a difference between the amplitudes of the output signals of the first and the second amplifier.
The invention can be used in all types of electric circuits, however, it can be particularly advantageously used to correct amplitude differences which may occur during demodulation of a radio frequency signal. Thus, the invention also relates to a receiving device for receiving a radio signal, which device comprises:
a quadratic module for supplying two output signals separated in phase by 90xc2x0, the phases of which are representative of data conveyed by the radio signal, and
a correction device for correcting a difference in amplitude between the output signals of the quadratic module,
which receiving device accommodates the correction device as described hereinabove.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.